Hydrocarbon and silicone fluids, e.g., oils, can provide electrical isolation between a stator and rotor and also power leads in an electric motor. Additionally, oils provide lubrication for engines and motors to extend lifetime and prevent failure. Motor oils lubricate surfaces in relative motion and close contact to one another, such as for example, bearings and other metal surfaces, to improve motor efficiency and motor run life. Additionally, oils can be useful for carrying away heat that is generated within the motor, thereby reducing the operating temperature.
A broad range of electrical resistivities, thermal conductivities, and fluid properties exist among oils. Oils are generally selected based upon a desired viscosity at a specified operating temperature. Preferably, oils are selected to ensure efficient operation of a motor or engine at desired operating temperatures by providing sufficient viscosity for lubrication.
Even for electrical devices without moving parts, heat transfer from static components and their electrical isolation are considerations, particularly in high voltage or high current applications. Additional equipment is sometimes needed to aid the cooling of these devices. New materials for electrical insulation and thermal conduction having suitable viscosities would be well-received in the art.